The invention relates to a shaving head comprising at least a first cutting member and a second cutting member which, viewed in a shaving direction of the shaving head, is arranged behind the first cutting member, said cutting members each comprising a plate-shaped carrier provided with a substantially straight cutting edge extending substantially in a skin contact surface with which, in operation, the shaving head bears against the skin to be shaved, and a cutting angle present between the second cutting member and the skin contact surface being equal to or larger than a cutting angle present between the first cutting member and the skin contact surface.
The invention also relates to a shaver comprising a handgrip and a shaving head secured to said handgrip, which shaving head is provided with at least a first cutting member and a second cutting member which, viewed in a shaving direction of the shaving head, is arranged behind the first cutting member, the cutting members each comprising a plate-shaped carrier provided with a substantially straight cutting edge extending substantially in a skin contact surface with which, in operation, the shaving head bears against the skin to be shaved, and a cutting angle present between the second cutting member and the skin contact surface being equal to or larger than a cutting angle present between the first cutting member and the skin contact surface.
A shaving head and a shaver of the types mentioned in the opening paragraphs are generally known and commonly used, particularly, respectively, in and as a razor. In a known shaving head, the plate-shaped carriers of the cutting members are arranged so as to be substantially parallel in a holder. The two main side faces of each of the carriers are sharpened substantially symmetrically, so that the cutting edges of the cutting members each have a tip angle which is substantially symmetrical with respect to a center plane of the carrier extending between the two main side faces of the carrier of the relevant cutting member. Thus, in the known shaving head, a substantially equal cutting angle is present between each cutting member and the skin contact surface, which cutting angle is defined as the acute angle enclosed between the skin contact surface and a bisector of the tip angle of the cutting edge of the relevant cutting member. A drawback of the known shaving head resides in that cut hairs and shaving foam collect in the comparatively narrow interspace between the parallel carriers of the cutting members. As a result, said interspace becomes clogged with the passage of time, causing the shaving performance of the known shaving head to be reduced substantially.
The above-mentioned drawback occurs to a larger extent in a shaving head disclosed in U.S. Pat. No. 4,562,644. In this known shaving head, the cutting angle between the skin contact surface and the second cutting member which, viewed in the shaving direction, is arranged behind the first cutting member, is larger than the cutting angle between the skin contact surface and the first cutting member. As a result, the skin smoothness that can be achieved using this known shaving head is comparatively high, and also the shaving comfort is comparatively high. This can be attributed to the fact that in the case of cutting members as applied in the known shaving head, the skin smoothness that can be achieved increases as the cutting angle between the cutting member and the skin contact surface increases. However, the shaving comfort decreases as the cutting angle increases, which can be attributed to the fact that the tensile forces exerted on the hairs increase. In the case of the shaving head known from U.S. Pat. No. 4,562,644, the hairs are first cut by the first cutting member. This cutting member has a comparatively small cutting angle as a result of which the hairs are shortened in a comparatively comfortable way. Subsequently, the hairs shortened by the first cutting member are shortened further by the second cutting member having a larger cutting angle, as a result of which a comparatively high skin smoothness is attained, which is characteristic of this larger cutting angle. The cutting of already shortened hairs by means of a cutting member having a comparatively large cutting angle is experienced by the user as much less painful, however, than the cutting of comparatively long hairs by means of such a cutting member, so that the known shaving head is experienced as comfortable by the user in spite of the comparatively large cutting angle of the second cutting member. As the cutting angle of the second cutting member is larger than the cutting angle of the first cutting member, an interspace is present, however, between the carriers of the two cutting members of this known shaving head, which interspace converges, viewed from the skin contact surface. As a result, in operation, cut hairs and shaving foam cause this interspace to become clogged comparatively rapidly.
It is an object of the invention to provide a shaving head and a shaver of the types mentioned in the opening paragraphs, wherein a cutting angle is present between the second cutting member and the skin contact surface, which cutting angle, like in the known shaving heads, is equal to or larger than the cutting angle present between the first cutting member and the skin contact surface, and wherein, however, the above-mentioned drawback of the known shaving heads is reduced as much as possible.
To achieve this object, a shaving head in accordance with the invention is characterized in that the cutting edge of at least one of the two cutting members is situated on a side, facing away from the other cutting member, of an imaginary center plane of the carrier of the relevant cutting member, said imaginary center plane extending between the two main side faces of the carrier.
To achieve this object, a shaver in accordance with the invention is characterized in that the shaving head used therein is a shaving head in accordance with the invention.
As the cutting edge of at least one of the two cutting members is situated on said side of the imaginary center plane, i.e. outside the imaginary center plane of the carrier of the relevant cutting member, the cutting edge of the relevant cutting member has a tip angle which is asymmetrical with respect to said center plane, so that the bisector of said tip angle encloses an angle with said center plane. As a result, the cutting angle of the relevant cutting member, which is determined by the acute angle enclosed between the skin contact surface and said bisector, differs from the acute angle enclosed between the skin contact surface and said center plane. As the cutting edge of the relevant cutting member is situated on the side of said center plane facing away from the other cutting member, it is achieved in an embodiment wherein the cutting angles of the two cutting members are equal, to provide an interspace between the carriers of the two cutting members which, viewed from the skin contact surface, is divergent. Said interspace has a divergence angle which is substantially equal to the angle between said bisector and said center plane. The risk of such a divergent interspace becoming clogged is much smaller than the risk of an interspace between two parallel carriers becoming clogged, as in the case of the above-mentioned known shaving head having cutting members with equal cutting angles. In an embodiment wherein the second cutting member has a larger cutting angle than the first cutting member, an interspace between the carriers of the cutting members is provided, as a result of said position of the cutting edge of at least one of the cutting members, which interspace, viewed from the skin contact surface, is less convergent or even divergent as compared to the above-mentioned shaving head known from U.S. Pat. No. 4,562,644. The risk of such a less convergent, or even divergent, interspace becoming clogged is much smaller than the risk of an interspace between two more convergent carriers becoming clogged, as in the case of the shaving head known from U.S. Pat. No. 4,562,644.
A particular embodiment of a shaving head in accordance with the invention is characterized in that the cutting edge of the relevant cutting member has a tip angle which is predominantly enclosed by a main side face, facing away from the other cutting member, of the carrier of the relevant cutting member and by a facet surface provided on a main side face, facing the other cutting members, of said carrier. In this particular embodiment, the cutting edge is provided on the relevant cutting member by providing a facet surface on only one side of the carrier. As a result, the cutting edge has a chisel-shaped tip angle. In this manner, the angle enclosed between the bisector of the tip angle and the imaginary center plane of the carrier is as large as possible. As a result, in an embodiment comprising cutting members having equal cutting angles, the interspace between the carriers of the cutting members has an even larger divergence angle or, in an embodiment wherein the second cutting member has a larger cutting angle than the first cutting member, an even less convergent, or even more divergent interspace between the carriers of the cutting members is provided.
A further embodiment of a shaving head in accordance with the invention is characterized in that the shaving head is provided with only two cutting members, the cutting edge of the first cutting member being situated on a side, facing away from the second cutting member, of the imaginary center plane of the carrier of the first cutting member, while the cutting edge of the second cutting member is situated on a side, facing away from the first cutting member, of the imaginary center plane of the carrier of the second cutting member. As the cutting edges of the cutting members are in said positions relative to the imaginary center planes of the carriers, the divergence angle of the interspace between the carriers is further increased in an embodiment comprising cutting members with equal cutting angles, or, in an embodiment where the second cutting member has a larger cutting angle than the first cutting member, an even less convergent, or even more divergent interspace between the carriers of the cutting members is obtained.
A still further embodiment of a shaving head in accordance with the invention is characterized in that the shaving head is provided with a third cutting member which, viewed in the shaving direction, is arranged behind the first and the second cutting member, a cutting angle present between the third cutting member and the skin contact surface being equal to or larger than a cutting angle present between the second cutting member and the skin contact surface, and the cutting edge of the second cutting member being situated substantially in the imaginary center plane of the carrier of the second cutting member, the cutting edge of the first cutting member, however, being situated on a side, facing away from the second cutting member, of the imaginary center plane of the carrier of the first cutting member, and the cutting edge of the third cutting member being situated on a side, facing away from the second cutting member, of the imaginary center plane of the carrier of the third cutting member. As a result, in an embodiment comprising three cutting members having equal cutting angles, an interspace is provided between the carriers of the first and the second cutting member as well as between the carriers of the second and the third cutting member, which interspace is divergent, viewed from the skin contact surface. In an embodiment wherein the cutting angle of the second cutting member is larger than the cutting angle of the first cutting member, and wherein the cutting angle of the third cutting member is larger than the cutting angle of the second cutting member, an interspace is provided between the carriers of the first and the second cutting member as well as between the carriers of the second and the third cutting member, which interspace, viewed from the skin contact surface, has a comparatively small convergence, or even exhibits a divergence.